The invention claimed and disclosed herein pertains to staplers, and in particular to automatic staplers for stapling a stack of sheets together.
Automatic staplers are well known in the art. Such staplers can either be stand-alone units, or they can be integrated into another device. These integrated staplers and other finishing devices are often referred to as xe2x80x9cin-linexe2x80x9d devices. For example, many imaging apparatus, such as photocopiers and printers, can be configured with an automatic stapler for the stapling together of sheets of finished product. Frequently a stapler in a photocopier or a printer is part of a sorter-stacker attachment which can be used to sort, stack and collate sheets of finished product. Examples of such attachment devices incorporating staplers are described in U.S. Pat. Nos. 5,542,655 and 5,269,503, incorporated herein by reference. In the typical stapling process, a wire staple is driven into the top of a sheet stack by a stapling head. An anvil adjacent the back side of the sheet stack crimps the staple to thereby secure the sheets in the stack into a bound unit. The staples are typically provided in the form of a strip of pre-formed staple blanks which are attached to one another by glue or resin.
A common problem encountered by most stapling devices is that of using a staple of the proper size to staple together the sheet stack. A staple is defined by two essentially parallel legs which are joined in spaced-apart relationship by a crown portion. The legs of the staple should be at least as long as the thickness of the sheet stack to be stapled, otherwise the staple fails of its essential purpose, i.e., of holding all sheets in the stack together. Further, the legs of the staple should be of such a length that after the staple is driven into the sheet stack, the free ends protrude a sufficient distance beyond the last sheet to allow the free ends to be crimped around the back side of the sheet stack. Preferably, the free ends are crimped using a forming anvil so that the free ends are directed back towards the last sheet in the sheet stack. This not only helps to secure all of the sheets in the stack together, but also hides the sharp free ends of the staple which can cause injury and damage if they are left protruding beyond the bottom sheet in the stack. However, if the legs of the staple are much longer than the thickness of the sheet stack, then when the crimp is formed the free ends can actually be driven back through the sheet stack to thus protrude through the first sheet in the stack, presenting a hazard to persons handling the stapled sheet stack. This phenomenon can also damage the stapling head or cause it to jam. An oversized staple can also cause damage to the sheets in the sheet stack.
To address this problem of using a staple of the proper length, some staplers can accept different sized staples in the stapler, but only one size of staple is available for use by the stapler at any given time. This process requires a user to remove any staples which may be in the stapler and insert staples of the perceived correct size. It also requires that the user somehow be aware of the size of staples currently in the stapler. For stand-alone staplers this process is a relatively minor inconvenience, but for automatic in-line staplers used in imaging apparatus the process becomes more involved, and may even require the process to be performed by a trained technician.
Another solution to the problem is addressed by the use of a staple-forming device which forms a staple of the desired length from a reel of wire contained within the stapling apparatus. Such stapling apparatus are usually found in imaging apparatus, such as photocopiers. Examples of such stapling apparatus are described in U.S. Pat. Nos. 4,318,555 and 5,938,388. The apparatus described in the ""555 patent is configured to form staples of two different lengths from two separate spools of wire. The apparatus described in the ""388 patent forms a staple of a determined length from wire, using a sensor which detects the thickness of the sheet pack to determine the length of the staple. While these stapling apparatus may address the problem of using a staple of the proper length, the apparatus are quite complex.
What is needed then is a stapler which achieves the benefits to be derived from similar prior art devices, but which avoids the shortcomings and detriments individually associated therewith.
The present invention provides for a stapling apparatus which can contain at least two different sizes of staples (i.e., staples having different leg lengths) and can make any of the (two or more) staples available for use at any given time without requiring a user to remove and install staples. The staple most appropriate for stapling a given sheet stack can be selected from among the different sized staples which are provided in the stapler. The staples can either be provided in a strip of pre-formed staples, or they can be formed from a flat stack of pre-cut lengths of wire stock. The stapler can be provided with a sensor or other means to determine or estimate the thickness of the sheet stack. The stapler can also be provided with a controller which can use information from the sensor or other means to determine which staple available in the stapler should be used, based on the thickness of the sheet stack and the leg length of the staple. The stapler can be a stand-alone unit, or it can be part of an imaging apparatus (such as a photocopier or a printer). When the stapler is part of a copier or a printer (generically, xe2x80x9cimaging devicexe2x80x9d), then the imaging device can be provided with a processor that can determine the number of pages in each sheet stack of a print job, and can also determine the media thickness of each sheet in the sheet stack. The processor can then determine the estimated thickness of the sheet stack, and this information can be used to select the staple most appropriate for stapling the sheet stack.
One embodiment of the present invention provides for a stapler for driving a staple into a sheet stack defined by a plurality of sheets. The stapler comprises a first cartridge configured to receive a first staple defined by a first leg length, and a second cartridge configured to receive a second staple defined by a second leg length. Preferably, the staples are provided to the cartridges in the form of strips of staples which are removably attached to one another. The stapler has a stapling head configured to drive the staples into the sheet stack. The stapler further includes a cartridge positioning actuator configured to selectively position either the first cartridge or the second cartridge in line with the stapling head. In one configuration the cartridge positioning actuator comprises a first solenoid having an extensible arm in mechanical communication with the first cartridge. The cartridge positioning actuator can further include a second solenoid having an extensible arm in mechanical communication with the second cartridge. In another configuration the cartridge positioning actuator comprises a linear motor having a body and a slide portion configured to slidably move with respect to the body, and the first cartridge is supported by the slide portion. The second cartridge can also be supported by the slide portion of the linear motor. It should be appreciated that the stapler can include more than two cartridges to thereby provide to a user of the stapler a wider selection of staples.
The stapler can further include a controller configured to actuate the cartridge positioning actuator in response to receiving an input signal. A sensor or other means configured to detect or estimate the thickness of the sheet stack can be provided. The sensor can generate a thickness signal in response to detecting the thickness of the sheet stack, and the controller can use the thickness signal as the input signal for actuating the cartridge positioning actuator. In this way the controller, in conjunction with the sensor, can determine which staple is the correct staple to use based on the thickness of the sheet stack, and the controller can then cause the appropriate staple cartridge to be moved into position for stapling (assuming the appropriate cartridge was not already in position).
The stapler can also be placed within an imaging apparatus which is configured to generate the sheet stack. The imaging apparatus can include a sheet counting device configured to count the number of sheets in the sheet stack and to generate a sheet count signal in response thereto. In this case, as an alternative to (or in addition to) using a sensor to measure the thickness of the sheet stack, the controller can use the sheet count signal as the input signal for actuating the cartridge positioning actuator. The sheet counting device can be a device configured to detect the number of sheets of media which are deposited into an output tray as the sheet stack is formed. The sheet counting device can also receive information from a user console associated with the imaging device, as for example when a user enters via a keypad the desired number of copies of an original to be generated by the imaging apparatus. The sheet count signal (i.e., the total number of sheets in a sheet stack) can be used to estimate the sheet stack height by multiplying the sheet count signal by an average media thickness. Alternatively, the sheet stack signal can be supplemented with media type information so that the height of the sheet stack can be more accurately determined. The media type information can be obtained from sensors which can detect the thickness or weight (and therefore the approximate thickness) of the media. The media type information can also be provided by a user via the user console.
Accordingly, the controller is generally configured to determine an approximate thickness of the sheet stack using the input signal (such as from a thickness measuring sensor) to determine which of the first and second cartridges contains a staple having a leg length most suited for stapling the sheet stack. The controller can then actuate the cartridge positioning actuator if the determined cartridge is not currently positioned in-line with the stapling head. Thereafter the controller can generate a xe2x80x9cstaplexe2x80x9d signal to actuate a stapling head actuator. The stapling head actuator is configured to cause the stapling head to drive the staple into the sheet stack in response to receiving the xe2x80x9cstaplexe2x80x9d signal.
Another embodiment of the present invention provides for a stapling apparatus for driving a staple into a sheet stack defined by a plurality of sheets. The stapling apparatus comprises a first stapler and a second stapler. The staplers each comprise respective first and second cartridges configured to receive respective first and second staples. The staples are defined by respective first and second leg lengths. The staplers further include respective first and second stapling heads configured to drive the respective first and second staples into the sheet stack. The stapling apparatus has a stapler positioning actuator configured to selectively position one of the first or the second stapler heads over a predetermined position on the sheet stack. The primary difference between the stapling apparatus just described and the stapler previously described is that in the latter stapling apparatus the stapling heads move along with the staple cartridges, whereas in the former stapler the staple cartridges move with respect to the stapling head. It should be understood that when I talk about positioning the selected staples over a xe2x80x9cpredetermined positionxe2x80x9d on the sheet stack I mean a position where the stapled is intended to be placed. This position can vary, such as when an in-line stapler is moved to staple the top or side of the sheet stack.
The stapler positioning apparatus in the stapling apparatus can comprises one of a solenoid or a linear motor, in a manner similar to that described above with respect to the stapler. Likewise, the stapling apparatus can include a controller, as well as associated components (such as a sheet stack thickness sensor), which can all function in a manner similar to that previously described. In this way the staplers can be automatically positioned over the sheet stack to thus present the appropriate staple for stapling the sheet stack.
As stated previously, a stapler in accordance with the present invention can be a stand-alone unit, or it can be incorporated into another apparatus, such as an imaging apparatus. Accordingly, a third embodiment of the present invention provides for an imaging apparatus configured to generate a stack of sheets of media bearing images and to deposit the stack of sheets of media in an output tray. The imaging apparatus comprises a stapler, which itself comprises a first cartridge configured to receive a first staple defined by a first leg length, and a second cartridge configured to receive a second staple defined by a second leg length. The stapler further includes a stapling head configured to drive the staples into the sheet stack, and a cartridge positioning actuator configured to selectively position one or the other of the first or the second cartridges over a predetermined position on the sheet stack. The stapler also has a stapling head configured to drive staples from the cartridge positioned over the predetermined position on the sheet stack into the sheet stack.
As with the stapler and the stapling apparatus previously described, the imaging apparatus can include a controller and associated components (such as a sheet stack thickness sensor) which can all function in a manner similar to that previously described. In this way the cartridges can be automatically positioned over the predetermined position on the sheet stack to thus present the appropriate staple for stapling the sheet stack.
A fourth embodiment of the present invention includes a method of stapling together a first stack of sheets of media. The method includes the step of providing a first strip of staples having legs defined by a first length, and providing a second strip of staples having legs defined by a second length. One of the first or the second strips of staples are then moved over a predetermined position on the first stack of sheets. The method includes detaching a staple from the strip of staples moved over the predetermined position on the stack of sheets and driving the staple through the stack of sheets. The method can also include measuring the thickness of the stack of sheets, and then selecting the strip of staples to be moved over the predetermined position on the stack of sheets based on the measured thickness. Alternately, rather than measuring the thickness of the stack of sheets, the method can include estimating the thickness of the stack of sheets, and then selecting the strip of staples to be moved over the predetermined position on the stack of sheets based on the estimated thickness.
Since the stapler can be provided in an imaging apparatus, as previously described, and since the imaging apparatus can be provided with a sorter to sort multiple copies of a document into separate sheet stacks, the method can thus include the step of moving the strips of staples to a location near a second stack of sheets. A staple from the strip of staples moved over the predetermined position on the second stack of sheets is then detached from the strip and is driven through the second stack of sheets.
These and other aspects and embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein: